<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<title></title>
	</head>
	<body>
		
	</body>
	<script>
	    let num1=123,num2='hello';
	    console.log(num1);
	    console.log(num2);
	    console.log(typeof(num1));   //打印数据类型
	    console.log(typeof(num2));
	    console.log(typeof('----------'));
	    let flag=true;
	    console.log(flag);
	    console.log(typeof(flag));
	    flag=false;
	    console.log(flag);
	    console.log(typeof(flag));
	    console.log('---------');
	    let str1='子曰："学而时习之"';
	    console.log(str1);
	    console.log(typeof(str1));
	    //子曰：'学而时习之'
	    //he said:'day day study';
	    //在字符型中，单引号中用单引号，或双引号中用双引号，需要用到转义符
	    let str2='he said:\'day day study\'';
	    console.log(str2);
	    console.log(typeof(str2));
	    str2="子曰：\“学而时习之\”";
	    console.log(str2);
	    console.log('------');
	    let Null=null;
	    console.log(Null);
	    console.log(typeof(Null));
	    console.log('--------');
	    let unNum;
	    console.log(unNum);
	    console.log(typeof(unNum));
		 let str3='';
		console.log(str3);
		console.log(typeof(str3));
	</script>
</html>
